The frequency range of the wireless mics will either be in VHF-low band like TXFirefighter said, or the may be up in 160-161 range. The higher-end mics from Shure and Sennheiser, for example, use many of the UHF TV channels in the 560-low 700 MHz range. Most of the time, these are out of range of traditional consumer scanners. Like TXFirefighter said earlier, just ask the sound guy. Having worked as a sound tech at my church for awhile, I know I'd be glad to relay this information if asked.
Dustin